Sail cloth has traditionally consisted of a weave of warp and weft threads. These threads lay transverse to one another, with the warp being the thread more capable of bearing the stresses than the weft.
Rather than being manufactured as a unitary piece, a sail is often constructed out of various panel layouts which are seamed together finally to construct a complete sail. Cutting the sail into panels allows the warp threads to be oriented in the direction of the various principal force lines, usually towards the boundary points of loading, i.e., attachment points of the sail to the vessel. These high load points include the head, the clew and the tack of the sail, where the loads are especially severe. However, in cutting the panels to approximate these principal force lines, the proper orientation is normally not achievable with woven cloth material. In addition, the warp threads "run off" the cloth, that is, the warp threads end at the edge of the panel, thus lacking any continuity along the force lines for any significant distance. This contributes to bias loading of the woven material. Woven material tends readily and sometimes (if laminated with a film) irreversibly distend when bias loaded.
Another disadvantage to a warp-weft technology lies in the potential for distention and weakness caused by the over and under nature of a woven material. Stretching and distortion of the material further result if the cloth is "off-parallel" and bias loaded to the weft direction. Certain processes may overcome this distortion, if the distortion is slight, including resinating the material, calendaring the material under heat conditions to stabilize the cloth, creating a very tight weave, laminating an isotopically resistant film, such as polyester film unto the cloth etc. However, most of these processes tend to be either material, labor, or capital intensive, and the approach of creating a tight weave results in an uneconomical use of thread in that only a certain percentage of the warp threads carry the actual load in addition to the relatively unused weft thread portion. Often the sail panels are tailored to reduce the bias behavior of the material, by narrowing the width of the panel at considerable increase in labor costs e.g. for sewing. Seams also introduce stress concentration wherever the needle punctures the sail material.
In U.S. Pat. No. 4,593,639 to Conrad, the inventor innovatively relieved the sail skin fabric of its primary role as "stress bearing member", by introducing stress-bearing structural members incorporated in the sail skin, in the form of fabric strips, yarns, monofilaments or laminate strips.
With U.S. Pat. No. 4,708,080 to Conrad, the concern over the warp, weft and cloth-panel orientation has been completely eliminated. Structural threads are predeterminedly located on each panel in a manner to achieve proper orientation of each of the threads in the panel and these threads are tied into a series of continuous catenaries for a sail.
Along with the simplified panel layout of a reduced number of panels, proper catenaries in the sail are formed in an improved manner thereby reducing the weight of the sail and improving its performance and durability. A monocoque construction of a sail is achieved by the proper joining of the principal or primary stress-bearing structural yarns in their catenary form in combination with the secondary structural elements, e.g., the grid members or scrim members.
More recently, U.S. Pat. No. 5,038,700 to Conrad, presents advances in the construction of light-weight sails, the corners of these sails, reef points for main-sails and other incorporated components in the sail, i.e., batten pockets, spreader patches and the like. Panels are made of a film with threads, foam, and film with or without threads. This last patent also discloses a wide variety of film and thread materials which may be useful. U.S. Pat. Nos. 4,593,639, 4,708,080 and 5,038,700 are incorporated by reference.
One attempt to overcome the problems associated with prior sail material bias distention of the sails has been presented by U.S. Pat. No. 5,001,003 to Mahr, which proposes a scrim of intersecting lines of yarn laminated between film and cloth, where the scrim is arranged to provide strength, integrity and stretch resistance to the sail material in the weft and bias directions. This technology still addresses the woven material problems and requires woven material substrates. Scrim comprised of parallel strands (i.e. warp and weft) and one knit strand was introduced as part of a laminated sail by U.S. Pat. No. 4,444,822 to Doyle et al.
Now that warp-weft direction of cloth and panel orientations are no longer a concern, the benefits of panel construction have changed accordingly. Rather than using panel layouts to align the warp threads with the load lines, the panel selection and layouts are now used as a method for optimizing the manufacturing of a sail appropriate for mass production, as well as a method for accurate laying of structural members in a sail, i.e., the primary and secondary structural members. Moreover, multiple laminates are also possible with the lamination schedule also adding to the necessary product enhancements.
U.S. Pat. No. 5,097,784 to Baudet reveals a method of sail-making in a unitary laminated piece. This method is costly and less attractive for mass production. A three dimensional mold is required on which only one sail is made. Each mold must be adjusted for each different sail as such method does not lend itself to broad seaming. Demand for an individual panel with a particular structural thread pattern in greater numbers than for other panels and different reinforcing patterns such as for reef points makes molded sails less suitable for flexible manufacturing and rapid changes. Hence, for an individual complete sail with a particular structural thread pattern, machine flexibility is highly desirable for thread variations in count, in size, in length and in layout pattern which cannot be achieved with a molded sail construction.
The quality of the product sail is diminished when made on a mold. Lamination problems occur when lamination is performed on the three dimensional mold. Further, although three dimensional mold techniques disclose applying tension to threads, these threads cannot be curved on the mold--it is believed impossible to do so unless the curved threads are restrained by pins.
By comparison, the present invention relates to a method and apparatus for manufacturing a sail panel for construction of a sail, with structural reinforcement threads incorporated in the sail panel in a large variety of complex and difficult patterns. In the present invention as well as the method presented in U.S. Pat. No. 4,708,080, threads are laid in tension across the sail skin through the use of pins around which the threads are looped. The pins not only provide the tension necessary to properly lay the threads down on the sail skin, but they also provide the direction necessary to lay accurately the threads down in their predetermined pattern.
In the prior art, known apparatus and methods include methods for manufacture of laminated reinforced film, for making fiber reinforced tape, for production of bias fabrics, warp knitting machines, and the like. Generally, prior art warp knitting machines have a weft insertion magazine which lays weft threads in parallel across the entire breadth of the machine and also has a substrate providing arrangement wherein the plane of the substrate subtends an acute angle with the plane of the weft thread and is further provided with at least one boundary element, in particular, a hold down means on the side of the substrate path opposite to the needle bar.
The thread is typically wound around certain elements, including a spindle, retractable element, needles and clamping means, and the like, before returning to their parallel path across the table. All of the known methods and apparatus relate to reinforcement means, threads, fibers, and the like that are laid out parallel to each other, failing to provide means for laying out reinforcement means, threads, fibers, and the like in non-parallel patterns.
In U.S. Pat. No. 4,052,239 to Chen, a fiber reinforced tape is manufactured by moving the tape through a first area while looping a thread on one side of the tape in a plane transverse to the direction of the movement of the tape. Each angled loop is held initially by a retractable pronged element and is then secured onto each end of the reinforced tape product by a vacuum belt, depositing the thread on the tape in a zig-zag pattern. Rollers such as heated roller then secure the thread to the tape. The apparatus described by Chen comprises a cross-belt moving in a closed loop transverse to the direction of the tape's movement, with the cross-belt having a carrier for the thread and looping means at each end of the cross-belt that move in and out of the plane of the thread as the thread is carried by the cross-belt. The machine can only produce a zig-zag pattern on the underlying film and not a varied pattern with convergent-divergent section, e.g. in the same panel, in opposite orientation to each other. A pressure belt is available to keep the loop ends in place, however actual adhesion occurs afterwards when the rollers secure the thread to the tape.
U.S. Pat. No. 4,397,703 to Osborn describes an apparatus for making a fiber-reinforced composite film sheet, which comprises a creel and fiber guides for forming the first lap of machine-direction fibers, and a pair of endlessly revolving roller chain assemblies supporting rows of spindles which are arranged to be initially interwoven, then divergent, and finally in parallel movement to form the second lap of transverse-direction fibers. This second lap of fibers are looped over selectively spaced-apart rows of spindles, and cam means are used to lift each row of loops from the spindles before lamination of film to the fibers. The machine is unable to create non parallel patterns of thread. It lays down threads that are substantially parallel to each other and cross threads that are at about 90.degree. to the machine direction threads.
U.S. Pat. No. 4,556,440 to Krueger describes an apparatus for production of bias fabrics which provides for a layer of parallel strands held together by external means (including, but not limited to stitching). The layer is formed at various angles relative to the long axis of the fabric and is wrapped around a series of needles formed on moving conveyors, maintaining the parallel orientation of the strands within. The machine is driven by an oscillating crank mechanism whose oscillating drive shaft moves more slowly before its direction is reversed, causing the movement of the yarn carrier to be naturally slowed at the end of each course. The yarn carrier is attached to an arm extending the width of the fabric, and the yarn carrier is attached to the arm and lays down a plurality of yarns with each sweep. The machine at all times lays down a parallel tow of strands or threads. It does not have the ability to lay down non-parallel threads and in opposite orientation in the non-parallel configuration.
Further inflexibilities in the apparatus are found since both conveyor belts move at a constant speed toward the bonding mechanism where the fabric layers are bound together. The conveyor belts are only capable of movement in one direction, and they cannot move independent of one another, nor at different speeds from each other. This limits the range of patterns that can be created by the mechanism.
U.S. Pat. No. 4,867,825 to Gidge describes an apparatus for forming cross-wise filaments for non-woven fabric which is subsequently further modified by length-wise direction filaments. The machines uses pins or grippers to put crosswise filaments in position to be adhered to edge elements. Pins are located on opposite ends of a table and in a center island that moves longitudinally along the table. Substantially parallel filaments are laid down by this machine. Gidge attempts to achieve a high degree of parallel uniformity by limiting the distances by which edge spacing pins can move, and by rigidly fixing the edge spacing pins relative to each other as a group.
U.S. Pat. No. 3,108,028 to Sprunck et al. describes an apparatus for the reinforcement of glass fibre webs or mats. According to the apparatus in Sprunck et al., a mat on a conveyor belt is reinforced by reinforcement means unravelled from a bobbin. Reinforcement means are blown by a stream of air from its holder into a gripper mouth. In the gripper mouth, the reinforcement means are stretched transversely across a mat at right angles to the direction of movement. The transverse reinforcing means, in a stretched-out position and in parallel relation, then rest on the mat. A band burner is ignited so that the transverse reinforcing means between the conveyor belt and the bobbins are melted at a position close to the edge of the conveyor belt. The gripper mouth then receives another feed of reinforcement means and returns across the mat for another pass. The result is the placement of strands across the mat in the undesirous form of individual and discontinuous strands.
U.S. Pat. No. 3,690,990 to Izumi describes an apparatus for manufacture of non-woven fabric. This apparatus reveals a means for extending yarns in a taught state in side-by-side parallel relation and equidistant from each other with other weft yarns about 90.degree. across the warp yarns. Yarn is ejected by a jet of air under high pressure by a yarn injecting device through a slit over warp yarns extended side-by-side and equidistant from each other. The intersections of the warp and weft yarns are interconnected by a heating press, and the weft yarn is then cut from its source by a cutter.
The apparatus described in U.S. Pat. No. 4,992,123 to Cave et al. presents a method for laying down a weft filament by propelling the filament through a chamber with an air gun over a moving substrate. The filaments are cut, clamped and pulled down onto the substrate. The apparatus propels the filaments by air and jet streams through an elongate hollow chamber across the substrate, a complex and questionably reliable method for laying down filament is involved. By pivoting the apparatus, the angles, at which the filaments can be laid onto the substrate, can be controlled. However, it is believed extremely difficult to propel a yarn impregnated with an adhesive. When the filament is clamped, it is pulled down through a closed aperture, then moved down onto the substrate while under tension once the aperture opens. Deposited on the substrate is the filament in the undesired form of an individual and discontinuous strand. In addition, absent from the apparatus in Cave et al. is a means to provide continuous, immediate and direct control of an adhesive coated filament as it travels across the substrate.
U.S. Pat. No. 4,804,436 to Debroche et al. describes a machine for the manufacture of a tire reinforcement cord yarn. The patent describes a tacky yarn fed to a device for receiving reinforcement cord that represents physically the path of the cord just before it touches the molded surface on which it is placed (i.e., a tire) and assures great precision of the laying of the cord. The device is formed of plates and located on opposite sides of the cord so as to assure a guidance of the cord. The device can be shaped so it can move the cord slightly away from its normal trajectory. The device also consists of flexible holding means so that the device can adjust to the curvature of the tire. The filaments however are laid out in parallel.
A method for making a composite component using a transverse tape is described in U.S. Pat. No. 4,938,824 to Youngkeit. This method comprises a laying of a flat tow at various angles across a conveyor belt to form a composite layer. Because the tow is flat, it is cut at each edge. The tow band consists of resin impregnated strand portions which are unwoven, unknitted and unstitched. If the tow were to turn around a pin, it would build up unwanted thickness, provide erratic turns, create a waste of material and cause uneven and poor fabrications of film--thread bonding.
Youngkeit fails to provide means for maintaining tension in the tow band because the tow band must be cut after placement of the tow band onto the base surface. Since the tow bands lie parallel to each other, there is no need in Youngkeit for pivot points around which strands are wrapped.
Australia Pat. No. 282,875 to Byrne presents a method and apparatus for obtaining reinforced web or sheet material or open mesh scrim. Individual strands or filaments are delivered and laid on top an advancing web or sheet material by at least two paired flying shuttles. The strands are laid out in transverse parallel relationship onto the web or sheet material.
In Canada Pat. No. 523,494 to Polley, lengths of parallel reinforcement thread are delivered in sucession and extended in parallel to one another across a paper web. The thread is delivered by two rotating members, one having a thread delivery head and the other a thread pickup head. A closeable jaw is located on the thread pickup head, and aids in keeping the thread taught upon receipt to ensure a clean and easy severance of the thread by a rotary cutter.
The apparatus described by Polley fails to provide continuous, immediate and direct control of threads as it travels across the paper web.
U.S. Pat. No. 4,550,045 to Hutson describes biased multi-layer structural fabric composites stitched in a vertical direction. Three layers of parallel fibers, with no secondary fibers in the plane of each layer, are laid down in the warp and weft stitching technology of Hutson. At least one of the layers is biased at certain angles. All of the threads are laid down in parallel in their respective layers. The fabric is saturated with a resin and cured. Three carriages lay down each layer of parallel fibers and a stitching machine stitches the layers together in the vertical direction, using a belt of hooks or needles at a sufficient height for the number of layers.
The apparatus described in Hutson requires careful coordination of the speed of the lay down carriage with the knitting machine and the means for advancing the fibers toward the stitching machine.
The apparatus described in U.S. Pat. No. 4,437,323 to Hittel et al. introduces a warp knitting machine having a weft thread magazine and a substrate provider for delivering the substrate along the substrate path. The magazine can transversely lay weft threads across the breadth of the machine again in parallel on the weft path upstream of the needle bed.
U.S. Pat. No. 3,823,049 to Vetrovec describes a rotary way of forming reinforced web with a zig-zag pattern of threads. Web is reinforced by glued warp and also can be bonded to a dry base strip. Loops around randomly arranged points are unobtainable. Only loops at consecutive points along the needles and the like are obtainable.
A method of manufacturing a flexible sheet material is achieved in U.S. Pat. No. 4,883,551 to Britton, by introducing a plurality of parallel strands by a weft laying device onto a paste-like bonding material deposited on an endless belt. Subsequent pluralities of strands are similarly introduced in the warp and weft directions atop each other. The material is finished upon curing by a heated roller. The apparatus is specifically designed for laying out all strands in substantial alignment with one another. This is done by the pivoting of a rail about an axle by a minimal angle determined by the weft laying device's (i.e., weft carriage) position as it completes a strand.
Sinusoidal waves can be created in a reinforced composite material as shown by the methods and apparatus in U.S. Pat. No. 4,398,650 to Holmes et al., U.S. Pat. No. 4,481,054 to Clausen et al., and U.S. Pat. No. 4,769,202 to Eroskey et al. In Holmes, sinusoidal waves are generated by a shaft that rotates a pin causing a reciprocating arm to move transverse to a corrugated medium.
The ability to generate sinusoidal waves is not suitable for the manufacture of sail panels for sail construction because strands in a sail panel must bear a load equally or be oriented in a catenary fashion, i.e., threads must be interconnected between point loads such as a tack, a clew and a head. A sail's efficiency in the wind increases with the ability to resist bulging or conversely the ability to be flattened. Since sinusoidal patterns in a sail panel would create a distortion, the sinusoidal generating apparatus presented in Holmes, Clausen and Eroskey is not suitable for making a sail material.